code: func (m *Manager) SetHosts(hosts []string) {
  	m.init()
  	m.mu.Lock()
  	m.state.Hosts = append(m.state.Hosts[:0], hosts...)
  	m.mu.Unlock()
  	m.updated()
  }
docs: // SetHosts sets the manager's list of known host names.
  // If the list is non-nil, the manager will only ever attempt to acquire
  // certificates for host names on the list.
  // If the list is nil, the manager does not restrict the hosts it will
  // ask for certificates for.