lib/net/textproto: patch Dial

_demo/mimeheader/mimeheader.go

@@ -0,0 +1,13 @@
+package main
+
+import "net/textproto"
+
+func main() {
+	h := make(textproto.MIMEHeader)
+	h.Set("host", "www.example.com")
+	println(h.Get("Host"))
+}
+
+/* Expected output:
+www.example.com
+*/