_ http2clientConnPoolIdleCloser = http2noDialClientConnPool{}
)

// TODO: use singleflight for dialing and addConnCalls?
type http2clientConnPool struct {
	t *http2Transport

	mu sync.Mutex // TODO: maybe switch to RWMutex
	// TODO: add support for sharing conns based on cert names
	// (e.g. share conn for googleapis.com and appspot.com)
	conns        map[string][]*http2ClientConn // key is host:port

    * The vSphere cloud provider has a cleanup function with a loop,
    * inside of which a write lock was intended to prevent races against
    * VM creation, but the usage of the sync.RWMutex type is incorrect,
    * plus is placed in a defer call so the locking is effectively
    * nonexistent.  This patch adds an anonymous function call inside
    * the loop to correctly handle acquiring the write lock with deferred

    * The vSphere cloud provider has a cleanup function with a loop,
    * inside of which a write lock was intended to prevent races against
    * VM creation, but the usage of the sync.RWMutex type is incorrect,
    * plus is placed in a defer call so the locking is effectively
    * nonexistent.  This patch adds an anonymous function call inside
    * the loop to correctly handle acquiring the write lock with deferred

</p>

<pre>
// A Mutex is a data type with two methods, Lock and Unlock.
type Mutex struct         { /* Mutex fields */ }
func (m *Mutex) Lock()    { /* Lock implementation */ }
func (m *Mutex) Unlock()  { /* Unlock implementation */ }

// NewMutex has the same composition as Mutex but its method set is empty.
type NewMutex Mutex