How To Use The Context Package In Golang?
Vložit
- čas přidán 6. 09. 2024
- ► Join my Discord community for free education 👉 / discord
► Become a Patreon for exclusive tutorials👉 / anthonygg_
► Follow me on Twitter 👉 / anthdm
► Follow me on GitHub 👉 github.com/anthdm
In this Golang tutorial, I will teach you how to use the context package for canceling slow-running tasks and how to share the state between functions having the same parent context.
#programming #golang
► Join my Discord community for free education 👉 discord.com/invite/bDy8t4b3Rz
► Become a Patreon for exclusive tutorials👉 www.patreon.com/anthonygg_
Thanks for watching
Context is like a bag or container that holds information that is shared between different parts of the program, especially when it comes to handling a request. This information can include things like timeouts, cancellation signals, and other data that is specific to that request.
For example, imagine you are building a web server that handles a lot of incoming requests. Each request has its own specific needs and requirements, such as a deadline for how long it should take to complete. The context allows you to keep track of these individual requirements for each request, and make sure that they are handled properly.
This is the best readable explanation I ever read. 🤝
😊😊
I've been putting off learning context because of its strange nature. You've cleared it up in 17 minutes, thank you.
You don't actually need the for loop for the select. Since you don't have a default case, the select with just block until a response is received or the context is canceled.
I also wandered the same thing.
I like how you're providing almost real life examples with such a passion! Your videos helped me A LOT!
Feels good to hear that! Much appreciate this comment
I have just started learning Go, there are lots of vids with basics but this sort of content gives you a good taste of what you actually should learn to become a good golang dev. Thanks a lot for your hard work!
Ty
Thanks Anthony your videos from last few days are helping a lot man. 🍻
Keep the content coming man, following along the JSON API series to write my own project has helped me learn Go so fast its unreal
Simplest and Effective Tutorial for Golang Context package! Thank you so much!!
I've been using Rust on my back end for web api / static file serving and it's great. I'm confident that after it compiles its going to run like a champ.... however, looking at how amazingly simple go code is and how beautiful concurrency is implemented I can't help thinking that I would be better off banging out web shit with Go. Rust, incredible power but as a solo dev the complexity weighs me down a bit. I feel like, from watching some of your vids I could be shipping code at light speed compared to what I'm able to do with Rust.
It always depends what you need. But as a solo dev Go is most likely a very good option because it's designed for fast development. I think in most cases Go is the better option. But if you for instance need really high performance web assembly like for a service like Figma then better go with Rust.
you are simply the best teacher i could ever have
The function fetchData alone is a perfect description of why Go is such a beautiful language and how much effort it actually takes away from you. Image, you would have to code all of these implicit functionalities (including something complex like coroutines, thread communication and sync) by yourself or take them from some repo and try to incorporate it into your project, in C++ for instance. Here, you get all of that, wrapped up in a nice syntax that it easy to understand and follow. :)
the best context tutorial I've ever seen!
Thank you
Literally the best explanation
Dude, that last application of a request ID in a context is the exact project I’m working on for work but in typescript. I wish we were making our APIs in GO but sadly not. I’ve been using a Axios wrapper inside a library I made and then in the request middleware I add the axios wrapper to an inversify config for dependencies injection. That way when ever a developer uses the axios wrapper in our code, all the classes have my axios wrapper with the request id as a public read only property. GO would be so much better
Great video, thanks so much! As for your remark about what language can do this so cleanly, I think C#'s CancellationToken implementation is as clean, or perhaps even cleaner as it can be passed to any task, and the cancellation token expiring can be handled by catching the exception thrown, which realistically is the only code you'd need to implement to get the equivalent of this code in Go.
next time you can consider using fmt.Errorf("some msg: %w", ctx.Err()) So the caller can rely on the embedded standard error to figure out it was a context related error on top of having a useful error message. Although, you could do all this stuff w/t the context package (func call with a cancel signaling), especially since generics has landed. this was not the in depth discussion i was looking for, but not your fault.
Please note that the go-routine will not be cancelled, but will run until it's ended naturally (or the program exits). This is default Go behavior and as far as I know there's no way to cancel it from outside the go-routine.
Your channel is pure Gold! Thanks for sharing your knowledge with the world!
Surely the best explanation of contexts I've ever seen, thx
Keep the videos coming!👏👏
You're a fantastic teacher, Anthony! Thanks for sharing your knowledge aways most smoothly and animatedly possible - I've learned heaps watching your videos
Hi. First I wanna say I really love your channel. Seems you really have a deep knowledge of Go.
I have one question. What is the reason you give a context.Background to fetchUserData and wrap it then inside the function with the context.WithTimeout? What were your thoughts behind this design decision ? why didn't you give the timeout context directly to the fetchUserData?
context code is explained well, but the infinite for loop is not placed well. it should be in a seperate goroutine as well
True true my bad
amazing video. I would love to see more about tracing, loging and grafana
Appreciate your content! Thanks so much!
Very educative!
How do you move around so fast, do you use vim bindings?
Yes. Vim bindings
Hey Anthony, great video, but wouldn’t the fetchThirdPartyStuff function keep running in the background after fetchUserData times out and returns?
I have had this happen in a very similar situation, but I used time.after instead of contexts.
Would this still happen with context timeouts if the whole program ran for longer?
you are right, i was wondering how there is no other comments that bring this up, the way it is done here the actual third party devil can stay alive indefinitely
Damn, that's scary 🤯
Perfect explanation. Thanks
@anthonygg_ why did we use infinite for loop to handle the select statement? That for loop will run only once and wait till the select statements are resolved and since select statement is terminating the function that infinite for loop seems unnecessary.
Ye my bad
Great video. Thanks Anthony!
Great Video. Loving your content.
Do you really need the select inside a for? In this case, isn't it going to work the same way if you remove the for?
No, was my mistake
very nice tutorial for who want starts golang. beautiful...
what the for loop is for?
Can be deleted, my bad.
Why for-select instead of only select?
For-select continuously monitors the channels
Yeah, otherwise it will fall through and the func will return if none of the channel operations are successful
It is done to make the function synchronise with the timeout of 150 ms; the empty for is a while true loop(which will block the function for any of the 2 cases to happen); and since we are guaranteed to receive from ctx.Done channel after some time T; it will synchronise the go routine; give it time to run
I'm still learning Go so I can't be sure. But a select without a default case is already blocking: it won't "fall through".
Actually, putting a loop around it only happens to work because he returns (exits the loop) in all cases, otherwise he'd deterministically run both cases (one after 150ms, one after 200ms) and then he'd wait eternally for a third message to any of the channels that is never sent.
Correct me if I'm wrong, but to me it looks like he's putting a loop around it because he's "used to" putting loops around channel stuff.
New to go. I didn't know about context and ended up making a struct to implement a shared state...
Great video sir❤❤❤
Anyone reading this: This is *exactly* what we do in my company. So if you are looking for stuff to learn to get hired, this is one of those things!
Hi Anthony! When we cancel a request with context to avoid a long wait for a response from a third-party server, does the mechanism also cancel the HTTP request operation at a low level (in a system call) ?
why infinite for loop was required ? select statement alone was sufficient. Select waits for one of the case channel operation to complete.
My mistake
Thank you for the good content
Very useful! Thanks! :)
cool video on context
Beautiful video, thanks!
you are awesome, thanks for these videos
WOW. Cool 🔥. Really cool 🔥. Appreciate it 🤝
great vid!
Great video! Cheers from Guatemala
Hey, thanks!
thankyou this was informational
Glad it was helpful!
you are awesome
😍
Can somebody explain what will happen with the goroutine? Will not it hang infinitely waiting for the response? How it will be killed?
think of it like 2 goroutine run simultaneously (one is context with timeout, one is request fetching). They both have channel to receive signal (or data).
Now we put 2 of them inside a select statement to basically check which one send the signal first. In case the context send first, that means the request is timeout
Came for contexts, stayed for the Swiss accent :)
wait go is really clean af wtf
I dont get why you wrapped select statement in for, since you return from each select branch?
loving it
thank u Great Man
thank you, great content. you talk like T Bag from prison break 😄
amazing
Great video….
The one thing I'm confused with is why does `context.WithTimeout()` & `context.WithValue()` need the `ctx` as parameter? What is it exactly? Why does that parameter matter?
And, why does `ctx` need to be initiated from the main function (instead of on the `fetchUserData` right away? I mean before you started using `context.WithValue`.
the `ctx` parameter is needed when creating new contexts because it will use that context as the "parent" context. The exact same reason why we need to pass in the `ctx` in fetchUserData. Because it could be that someone already has a context created with some values attached to it, so we can read that deeper in the stack without worrying about sharing a state that is unprotected by mutex guards. Values passed in the context are always safe to read from in other functions using that context as the parent. I hope this clears up your question.
ctx designed to be immutable, that’s why when adding new value/attribute(timeout, etc), you’re essentially creating new context based on last context plus whatever new attribute you’re adding
Apologies if I've missed this in this video or another video of yours but I'm struggling to work out how to test something similar to this.
I have a AWS Lambda function written in go that has basic GET/PUT/POST/DELETE handlers that use context. The function just read/writes to DynamoDB. My function works but I'm struggling to work out how to unit test my handlers. I likely just need to rewatch this and do more digging but if you have anything or anyone can link to some examples that might help then I'd really appreciate it.
(16:00) How does one actually implement request tracing in grafana?
Thinking about it, Would love a clip about integrating projects grafana / prometheus, pprof / opentelemetry etcetera :)
nice
I like how the go makes it so cluttered to implement a piece of code which does exactly what a CancellationToken would do in c# in ~6 loc
omg you are ao cool🤩
I'm not sure why the select statement needed to be ran in a for loop
Not needed . My mistake
very good
I think the for around select is extranous. You could have the same results without it
Jup. Little happy accident
I am struggling to understand the difference between context.WithDeadline and context.WithTimeout. they essentially do the same thing right ?
Yes, dont worry about it.
🤩
Hey, thanks for videos!
Can you please share your VS Code theme?
Gruvbox is the theme Im using
nice vids
Do you still need to use context pkg if you deploy this inside a service mesh like istio, which can handle timeouts in its envoy sidecars?
Is it possiblo to trigger a "cancel" on demand? I mean, what if you want to "cancel" a request not because the timeout, but because another arbitrary reason?
You can just call the Cancel thats returned from creating a new context. Cancel()
@@anthonygg_ :mmmm: I'm gonna try that
So in typescript world this would be a promise.race with the fetchTerribleSlowFunction and setTimeout promise ?
Hey Athony, could you please share how you use vim in your normal stuff? I really love your speed with vim. I've used vim for about 2 months but my speed really bad. I want high speed vimmer like you 😂
you could go watch some primagen’s videos about vim
@@what1heh3ck thanks
Can somebody explain why do we need an infinite loop with select? Why not just select?
A little happy accident of me
I’m a chess player, hey, that’s not true😂😂😂
> which language can those that, that clean?
> * silence *
> NONE exactly
loved that part
what theme?
Where can I get the code?
Great video but your keyboard / navigating stresses me out.
cancellation token in c# is much more reasonable
it's just a map it's really easy
boring lecture
Timmy
Excellent Video, thanks @anthonygg_ really appreciate your content.
I am new to Microservices and how they can be connected in Golang. Can I ask if you have any video in which you join Microservice together in one app. Something like a part 2 for "How to build and structure a go microservice"
Thank you for your help! U r making a great job!