Contextcontext.Context( UndoneContext) Deadline() (deadline time.Time, ok bool)( UndoneContext) Done() <-chan struct{}( UndoneContext) Err() error
Value returns the value associated with this context for key, or nil
if no value is associated with key. Successive calls to Value with
the same key returns the same result.
Use context values only for request-scoped data that transits
processes and API boundaries, not for passing optional parameters to
functions.
A key identifies a specific value in a Context. Functions that wish
to store values in Context typically allocate a key in a global
variable then use that key as the argument to context.WithValue and
Context.Value. A key can be any type that supports equality;
packages should define keys as an unexported type to avoid
collisions.
Packages that define a Context key should provide type-safe accessors
for the values stored using that key:
// Package user defines a User type that's stored in Contexts.
package user
import "context"
// User is the type of value stored in the Contexts.
type User struct {...}
// key is an unexported type for keys defined in this package.
// This prevents collisions with keys defined in other packages.
type key int
// userKey is the key for user.User values in Contexts. It is
// unexported; clients use user.NewContext and user.FromContext
// instead of using this key directly.
var userKey key
// NewContext returns a new Context that carries value u.
func NewContext(ctx context.Context, u *User) context.Context {
return context.WithValue(ctx, userKey, u)
}
// FromContext returns the User value stored in ctx, if any.
func FromContext(ctx context.Context) (*User, bool) {
u, ok := ctx.Value(userKey).(*User)
return u, ok
}
UndoneContext : context.Context
func UndoContext(ctx context.Context) UndoneContext