don't use -race with coverage, don't cover with -race

given the way we present output, we are redundantly running tests with
-race, which will make tests run unnecessarily longer, especially for
older versions of Go.

.travis.yml

@@ -17,7 +17,7 @@ before_install:
   - go get -t -v ./...
 
 script:
-  - ./go.test.sh
+  - ./go.coverage.sh
   - gometalinter --disable-all --enable=errcheck --enable=vet --enable=vetshadow --enable=megacheck --exclude=S1024 # TODO: remove exclude when we stop support Go 1.7 and lower
   - gometalinter --disable-all --enable=errcheck --enable=vet --enable=vetshadow --enable=megacheck --exclude=U1000 examples/... # the way examples are structured produces unused functions
   - gometalinter --disable-all --enable=errcheck --enable=vet --enable=vetshadow --enable=megacheck helpers/...

go.coverage.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+
+set -e
+echo > coverage.txt
+
+for d in $(go list ./... | grep -v -E '/vendor|/examples|/docker'); do
+    go test -coverprofile=profile.out -covermode=atomic "$d"
+    if [ -f profile.out ]; then
+        cat profile.out >> coverage.txt
+        rm profile.out
+    fi
+done

go.test.sh

@@ -1,12 +1,7 @@
 #!/usr/bin/env bash
 
 set -e
-echo > coverage.txt
 
 for d in $(go list ./... | grep -v -E '/vendor|/examples|/docker'); do
-    go test -race -coverprofile=profile.out -covermode=atomic $d
-    if [ -f profile.out ]; then
-        cat profile.out >> coverage.txt
-        rm profile.out
-    fi
+    go test -race "$d"
 done