cli/compose: use strings.Cut

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli/compose/convert/service.go

@@ -427,11 +427,11 @@ func uint32Ptr(value uint32) *uint32 {
 // convertExtraHosts converts <host>:<ip> mappings to SwarmKit notation:
 // "IP-address hostname(s)". The original order of mappings is preserved.
 func convertExtraHosts(extraHosts composetypes.HostsList) []string {
-	hosts := []string{}
+	hosts := make([]string, 0, len(extraHosts))
 	for _, hostIP := range extraHosts {
-		if v := strings.SplitN(hostIP, ":", 2); len(v) == 2 {
+		if hostName, ipAddr, ok := strings.Cut(hostIP, ":"); ok {
 			// Convert to SwarmKit notation: IP-address hostname(s)
-			hosts = append(hosts, fmt.Sprintf("%s %s", v[1], v[0]))
+			hosts = append(hosts, ipAddr+" "+hostName)
 		}
 	}
 	return hosts