Exclude go1.13.x from modules off, only build all on go1.13 modules on

.travis.yml

@@ -7,6 +7,10 @@ env:
   - GO111MODULE=off
 go: [1.11.x, 1.12.x, 1.13.x]
 os: [linux, osx]
+matrix:
+  exclude:
+    - go: 1.13.x
+      env: GO111MODULE=off ## Modules are the default now.
 install:
   - ./travis/install.sh
 script:

travis/cross_build.sh

@@ -1,5 +1,5 @@
 #!/bin/bash
 
-if [[ "$TRAVIS_GO_VERSION" =~ ^1\.12\. ]] && [[ "$TRAVIS_OS_NAME" == "linux" ]]; then
+if [[ "$TRAVIS_GO_VERSION" =~ ^1\.13\. ]] && [[ "$TRAVIS_OS_NAME" == "linux" ]] && [[ "$GO111MODULE" == "on" ]]; then
     $(go env GOPATH)/bin/gox -build-lib
 fi

travis/install.sh

@@ -2,7 +2,8 @@
 
 set -e
 
-if [[ "$TRAVIS_GO_VERSION" =~ ^1\.12\. ]] && [[ "$TRAVIS_OS_NAME" == "linux" ]]; then
+# Only do this for go1.12 when modules are on so that it doesn't need to be done when modules are off as well.
+if [[ "$TRAVIS_GO_VERSION" =~ ^1\.13\. ]] && [[ "$TRAVIS_OS_NAME" == "linux" ]] && [[ "$GO111MODULE" == "on" ]]; then
     GO111MODULE=off go get github.com/dgsb/gox
 fi
 
@@ -11,5 +12,6 @@ if [[ "$GO111MODULE" ==  "on" ]]; then
 fi
 
 if [[ "$GO111MODULE" == "off" ]]; then
-    go get github.com/stretchr/testify/assert golang.org/x/sys/unix github.com/konsorten/go-windows-terminal-sequences
+    # Should contain all regular (not indirect) modules from go.mod
+    go get github.com/stretchr/testify golang.org/x/sys/unix github.com/konsorten/go-windows-terminal-sequences
 fi