code: func (m *Memberlist) probeNodeByAddr(addr string) {
  	m.nodeLock.RLock()
  	n := m.nodeMap[addr]
  	m.nodeLock.RUnlock()
  
  	m.probeNode(n)
  }
docs: // probeNodeByAddr just safely calls probeNode given only the address of the node (for tests)