Update SDK's CI to ensure Go packages all compile (#1102)

Ensures all packages that are not excluded via build tags have non-test Go files in them. This ensures other CI tasks such as `go install` do not fail due to missing non-test Go files.

.travis.yml

@@ -25,6 +25,12 @@ matrix:
       - go: tip
 
   include:
+    - language: go
+      os: linux
+      go: 1.15.x
+      script:
+        - make go-build-modules-.
+
     - language: go
       os: windows
       go: 1.15.x

Makefile

@@ -86,7 +86,7 @@ tidy-modules-%:
 	@# module testing will start from. Strips off the "tidy-modules-" and
 	@# replaces all "_" with "/".
 	@#
-	@# e.g. build-modules-internal_protocoltest
+	@# e.g. tidy-modules-internal_protocoltest
 	cd ./internal/repotools/cmd/eachmodule \
 		&& go run . -p $(subst _,/,$(subst tidy-modules-,,$@)) ${EACHMODULE_FLAGS} \
 		"go mod tidy"
@@ -183,6 +183,18 @@ build-modules-%:
 		&& go run . -p $(subst _,/,$(subst build-modules-,,$@)) ${EACHMODULE_FLAGS} \
 		"go test ${BUILD_TAGS} ${RUN_NONE} ./..."
 
+go-build-modules-%:
+	@# build command that uses the pattern to define the root path that the
+	@# module testing will start from. Strips off the "build-modules-" and
+	@# replaces all "_" with "/".
+	@#
+	@# Validates that all modules in the repo have buildable Go files.
+	@#
+	@# e.g. go-build-modules-internal_protocoltest
+	cd ./internal/repotools/cmd/eachmodule \
+		&& go run . -p $(subst _,/,$(subst go-build-modules-,,$@)) ${EACHMODULE_FLAGS} \
+		"go build ${BUILD_TAGS} ./..."
+
 test: test-modules-.
 
 test-race-modules-%:

service/ec2/internal/customizations/doc.go

@@ -0,0 +1,3 @@
+// Package customizations provides the implementation of customizations for
+// the ec2 module.
+package customizations

service/s3/internal/configtesting/doc.go

@@ -0,0 +1,2 @@
+// Package configtesting provides unit testing of s3 module's config loading.
+package configtesting