Added GOOS={linux,darwin,windows} to the Travis-CI build matrix

.travis.yml

@@ -3,4 +3,18 @@ go:
   - 1.1
   - 1.2
   - 1.3
-script: go test -bench=.
+env:
+  # "gvm update" resets GOOS and GOARCH environment variable, workaround it by setting
+  # BUILD_GOOS and BUILD_GOARCH and overriding GOARCH and GOOS in the build script
+  global:
+    - BUILD_GOARCH=amd64
+  matrix:
+    - BUILD_GOOS=linux
+    - BUILD_GOOS=darwin
+    - BUILD_GOOS=windows
+script:
+  - gvm cross $BUILD_GOOS $BUILD_GOARCH
+  - GOARCH=$BUILD_GOARCH GOOS=$BUILD_GOOS go build
+
+  # only test on linux
+  - if [ $BUILD_GOOS == "linux" ]; then GOARCH=$BUILD_GOARCH GOOS=$BUILD_GOOS go test -bench=.; fi