Add custom map and range snippets for go-mode

snippets/go-mode/map

@@ -0,0 +1,5 @@
+# -*- mode: snippet -*-
+# name: map
+# key: map
+# --
+map[${1:type}]${0:type}

snippets/go-mode/range

@@ -0,0 +1,7 @@
+# -*- mode: snippet -*-
+# name: for range
+# key: range
+# --
+for ${1:k}, ${2:v} := range $3 {
+	$0
+}