something you don’t know about
Golang context

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object vs context

郭學聰 Hsueh-Tsung KuoSun, 18 Aug 2019

something you don’t know about Golang context object vs context 郭學聰 Hsueh-Tsung Kuo Sun, 18 Aug 2019

	t = Thread.new {
	(1..5).each {
	puts('hello')
	sleep(1.0)
	}
	}
	t.terminate()
	t.join()

	Thread t = new Thread(new ThreadStart(object.Method));
	t.Start();
	t.Abort();
	t.Join();

	import "context"

	parentCtx := context.Background()
	childCtx, cancel := context.WithCancel(parentCtx)

	go function(ctx context.Context, param1 int, param2 string) error {
	for {
	select {
	case <-ctx.Done():
	return ctx.Err()
	default:
	doSomething()
	}
	}
	}(childCtx, param1, param2)

	cancel()

	// init
	parentCtx := context.Background()

	// map (goroutine scope variable)
	// store goroutine scope variable
	childCtx := context.WithValue(parentCtx, key, value)
	value, ok := childCtx.Value(key).(ValueType)

	// control
	// get cancel button
	childCtx, cancel := context.WithCancel(parentCtx)
	// get cancel button and set deadline
	childCtx, cancel := context.WithDeadline(parentCtx, deadline)
	// get cancel button and set timeout
	childCtx, cancel := context.WithTimeout(parentCtx, timeout)

	type contextKey int

	const (
	contextKeySessionData = contextKey(1)
	)

	contextWithSessionData := context.WithValue(r.Context(), contextKeySessionData, sessionData)

	sessionData, ok := r.Context().Value(contextKeySessionData).(*AuthSessionData)

something you don’t know about
Golang context

who am I?

outline

process/thread/fiber

common

process

thread

fiber

goroutine

goroutine?

M:N threading

control process/thread/fiber/goroutine

id

object

goroutine

somehow idiomatic solution

context

context?

map (goroutine scope variable)

control

issues

start/terminate/join

join

the elegant(?) solution

conclusion

principle

comment

reference

commercial

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	import "sync"

	var wg sync.WaitGroup

	wg.Add(1)

	go function() {
	defer wg.Done()
	doSomething()
	}()

	wg.Wait()

	func HandlerFunc(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	resource.Connect(ctx, param1, param2)
	...
	}