Golang Context

timer *time.Timer

// newCancelCtx returns an initialized cancelCtx.

newCancelCtx(parent Context) cancelCtx

cancelCtx

bCtx

Done() <-chan struct{}

mu sync.Mutex

如果当前 deline 比新的早

childer map[canceler]struct{}

done chan struct{}

String() string

// propagateCancel arranges for child to be canceled when parent is.

timerCtx

valueCtx

Background() Context

// removeChild removes a context from its parent.

Context

deadline time.Time

removeFromParent == true

Value(key interface{}) interface{}

parent

func newCancelCtx(parent Context) cancelCtx { return cancelCtx{Context: parent}}

err error

var (    background = new(emptyCtx)    todo       = new(emptyCtx))

// parentCancelCtx follows a chain of parent references until it finds a// *cancelCtx. This function understands how each of the concrete types in this// package represents its parent.

TODO() Context

???

Err() error

emptyCtx

func (c *timerCtx) String() string {    return contextName(c.cancelCtx.Context) + \".WithDeadline(\" +        c.deadline.String() + \" [\" +        time.Until(c.deadline).String() + \"])\"}

func (c *valueCtx) Value(key interface{}) interface{} {    if c.key == key {        return c.val    }    return c.Context.Value(key)}

func (c *valueCtx) String() string {    return contextName(c.Context) + \".WithValue(type \" +        reflectlite.TypeOf(c.key).String() +        \