fix(tests): try to get code coverage from all packages

scripts/gocover.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+
+set -e
+
+echo "" > coverage.txt
+
+for d in $(go list ./... | grep -v github.com/prymitive/karma/internal/mapper); do
+    go test \
+        -coverprofile=profile.out \
+        -coverpkg=$(go list ./... | grep -v github.com/prymitive/karma/internal/mapper | tr '\n' ',') \
+        $d 2>&1 | grep -v 'warning: no packages being tested depend on matches for pattern'
+    if [ -f profile.out ]; then
+        cat profile.out >> coverage.txt
+        rm profile.out
+    fi
+done