upgrade to go1.15.5

.travis.yml

@@ -3,7 +3,7 @@ services:
     - docker
 language: go
 go:
-  - 1.14.x
+  - 1.15.x
 env:
   global:
     - TOOLS_CMD=golang.org/x/tools/cmd

Makefile

@@ -15,7 +15,7 @@ else
 endif
 
 # Go version to use for builds
-GO_VERSION=1.14.6
+GO_VERSION=1.15.5
 
 # K8s version used for Makefile helpers
 K8S_VERSION=v1.6.6

go.mod

@@ -1,6 +1,6 @@
 module github.com/coreos/flannel
 
-go 1.14
+go 1.15
 
 require (
 	cloud.google.com/go v0.9.1-0.20170629112852-7c205da84d8d // indirect