Fix concurrency issues (#12)

Author: mkenney

.travis.sh

@@ -4,7 +4,7 @@ set -e
 rm -f coverage.txt
 for dir in $(go list ./...); do
     echo "go test -timeout 20s -coverprofile=profile.out $dir"
-    go test -timeout 20s -coverprofile=profile.out $dir
+    go test -race -timeout 20s -coverprofile=profile.out $dir
     exit_code=$?
     if [ "0" != "$exit_code" ]; then
         exit $exit_code

.travis.yml

@@ -20,6 +20,7 @@ go:
     - 1.8.x
     - 1.9.x
     - 1.10.x
+    - 1.11.x
     - tip
 
 script: