Context / Context with value / Essential Go
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package main
import (
"context"
"fmt"
)
type User struct {
Name string
IsLoggedIn bool
}
type userKeyType int
var userKey userKeyType
func contextWithUser(ctx context.Context, user *User) context.Context {
return context.WithValue(ctx, userKey, user)
}
// returns nil if not set
func getUserFromContext(ctx context.Context) *User {
user, ok := ctx.Value(userKey).(*User)
if !ok {
return nil
}
return user
}
// will panic if not set
func mustGetUserFromContext(ctx context.Context) *User {
return ctx.Value(userKey).(*User)
}
func printUser(ctx context.Context) {
user := getUserFromContext(ctx)
fmt.Printf("User: %#v\n", user)
}
func main() {
ctx := context.Background()
user := &User{
Name: "John",
IsLoggedIn: false,
}
ctx = contextWithUser(ctx, user)
printUser(ctx)
}
Go
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