Update go.mod with expected Go compiler version

JensRantil · web-flow · commit de844847de93 · 2020-03-07T14:02:33.000-06:00
Pin the expected compiler version. This shouldn’t break backwards compatibility.
diff --git a/go.mod b/go.mod
@@ -1 +1,3 @@
 module github.com/jordan-wright/email
+
+go 1.13

Original file line number	Diff line number	Diff line change
`@@ -1 +1,3 @@`
`1`	`1`	`module github.com/jordan-wright/email`
	`2`	`+`
	`3`	`+go 1.13`