http2.getClientConn.go

func (p *http2clientConnPool) getClientConn(req *Request, addr string, dialOnMiss bool) (*http2ClientConn, error) {
  // more codes
  p.mu.Lock()
  for _, cc := range p.conns[addr] {
    if st := cc.idleState(); st.canTakeNewRequest {
      p.mu.Unlock()
      return cc, nil
    }
  }
  // more codes
}

func (cc *http2ClientConn) idleState() http2clientConnIdleState {
  cc.mu.Lock()
  defer cc.mu.Unlock()
  return cc.idleStateLocked()
}