Method handshakeContext

conn.go:1684–1755

(ctx context.Context)

}

func (c *Conn) handshakeContext(ctx context.Context) (ret error) {
	// Fast sync/atomic-based exit if there is no handshake in flight and the
	// last one succeeded without an error. Avoids the expensive context setup
	// and mutex for most Read and Write calls.
	if c.handshakeComplete() {
		return nil
	}

	handshakeCtx, cancel := context.WithCancel(ctx)
	// Note: defer this before starting the "interrupter" goroutine
	// so that we can tell the difference between the input being canceled and
	// this cancellation. In the former case, we need to close the connection.
	defer cancel()

	// Start the "interrupter" goroutine, if this context might be canceled.
	// (The background context cannot).
	//
	// The interrupter goroutine waits for the input context to be done and
	// closes the connection if this happens before the function returns.
	if ctx.Done() != nil {
		done := make(chan struct{})
		interruptRes := make(chan error, 1)
		defer func() {
			close(done)
			if ctxErr := <-interruptRes; ctxErr != nil {
				// Return context error to user.
				ret = ctxErr
			}
		}()
		go func() {
			select {
			case <-handshakeCtx.Done():
				// Close the connection, discarding the error
				_ = c.conn.Close()
				interruptRes <- handshakeCtx.Err()
			case <-done:
				interruptRes <- nil
			}
		}()
	}

	c.handshakeMutex.Lock()
	defer c.handshakeMutex.Unlock()

	if err := c.handshakeErr; err != nil {
		return err
	}
	if c.handshakeComplete() {
		return nil
	}

	c.in.Lock()
	defer c.in.Unlock()

	c.handshakeErr = c.handshakeFn(handshakeCtx)
	if c.handshakeErr == nil {
		c.handshakes++
	} else {