code: func (c *Client) SetThumbprint(host string, thumbprint string) {
  	host = hostAddr(host)
  
  	c.hostsMu.Lock()
  	if thumbprint == "" {
  		delete(c.hosts, host)
  	} else {
  		c.hosts[host] = thumbprint
  	}
  	c.hostsMu.Unlock()
  }
docs: // SetThumbprint sets the known certificate thumbprint for the given host.
  // A custom DialTLS function is used to support thumbprint based verification.
  // We first try tls.Dial with the default tls.Config, only falling back to thumbprint verification
  // if it fails with an x509.UnknownAuthorityError or x509.HostnameError
  //
  // See: http.Client.Transport.DialTLS