travis: update go version.

warpfork · warpfork · commit 823d4c176b60 · 2021-03-10T10:56:39.000+01:00
We'll need something a little more recent than 1.11.x to be able to
use the fmt "%w" and errors.Is features.
diff --git a/.travis.yml b/.travis.yml
@@ -4,7 +4,7 @@ os:
 language: go
 
 go:
-  - 1.11.x
+  - 1.15.x
 
 env:
   global:

-Original file line number
+Diff line change
 language: go
 go:
 -  - 1.11.x
 +  - 1.15.x
 env:
   global: