added round_robin, least_conn and ip_hash load balance support, small refactoring

internal/net/http/loadbalancer/mode.go

@@ -0,0 +1,29 @@
+package loadbalancer
+
+import (
+	U "github.com/yusing/go-proxy/internal/utils"
+)
+
+type Mode string
+
+const (
+	RoundRobin Mode = "roundrobin"
+	LeastConn  Mode = "leastconn"
+	IPHash     Mode = "iphash"
+)
+
+func (mode *Mode) ValidateUpdate() bool {
+	switch U.ToLowerNoSnake(string(*mode)) {
+	case "", string(RoundRobin):
+		*mode = RoundRobin
+		return true
+	case string(LeastConn):
+		*mode = LeastConn
+		return true
+	case string(IPHash):
+		*mode = IPHash
+		return true
+	}
+	*mode = RoundRobin
+	return false
+}