Bump golang 1.13 (#522)

*: bump Go version to 1.13
* Fix go.mod and vendor/

Signed-off-by: Simon Pasquier <[email protected]>

Author: simonpasquier

.promu.yml

@@ -1,7 +1,7 @@
 go:
     # Whenever the Go version is updated here, .travis.yml and
     # .circle/config.yml should also be updated.
-    version: 1.12
+    version: 1.13
 repository:
     path: github.com/prometheus/blackbox_exporter
 build:

.travis.yml

@@ -5,7 +5,7 @@ language: go
 # Whenever the Go version is updated here, .circleci/config.yml and .promu.yml
 # should also be updated.
 go:
-- 1.12.x
+- 1.13.x
 
 go_import_path: github.com/prometheus/blackbox_exporter
 

go.mod

@@ -19,3 +19,5 @@ require (
 	gopkg.in/yaml.v2 v2.2.2 // indirect
 	gopkg.in/yaml.v3 v3.0.0-20190502103701-55513cacd4ae
 )
+
+go 1.13