Upgrade gin-gonic to latest master, fix compatibility issues

vendor/github.com/gin-gonic/gin/examples/auto-tls/example1.go

@@ -0,0 +1,19 @@
+package main
+
+import (
+	"log"
+
+	"github.com/gin-gonic/autotls"
+	"github.com/gin-gonic/gin"
+)
+
+func main() {
+	r := gin.Default()
+
+	// Ping handler
+	r.GET("/ping", func(c *gin.Context) {
+		c.String(200, "pong")
+	})
+
+	log.Fatal(autotls.Run(r, "example1.com", "example2.com"))
+}