retry.go
func getHost(hostPort string) string {
	for i := 0; i < len(hostPort); i++ {
		if hostPort[i] == ':' {
			return hostPort[:i]
		}
	}
	return hostPort
}
func getHost(hostPort string) string {
	for i := 0; i < len(hostPort); i++ {
		if hostPort[i] == ':' {
			return hostPort[:i]
		}
	}
	return hostPort
}
// getHost returns the host part of a host:port. If no ':' is found, it returns the
// original string. Note: This hand-rolled loop is faster than using strings.IndexByte.