.github/workflows/ci.yml

@@ -0,0 +1,21 @@
+on: [push, pull_request]
+name: CI
+jobs:
+  test:
+    strategy:
+      matrix:
+        go-version: [1.17.x]
+        os: [ubuntu-latest, macos-latest, windows-latest]
+    runs-on: ${{ matrix.os }}
+    steps:
+    - name: Install Go
+      uses: actions/setup-go@v2
+      with:
+        go-version: ${{ matrix.go-version }}
+    - name: Checkout code
+      uses: actions/checkout@v2
+    - name: Test
+      run: |
+        #go vet ./...
+        go test -v -race ./...
+        go test -bench=.

go.mod

@@ -0,0 +1,3 @@
+module github.com/deckarep/golang-set
+
+go 1.17

threadunsafe.go

@@ -76,6 +76,9 @@ func (set *threadUnsafeSet) Contains(i ...interface{}) bool {
 
 func (set *threadUnsafeSet) IsSubset(other Set) bool {
 	_ = other.(*threadUnsafeSet)
+	if set.Cardinality() > other.Cardinality() {
+		return false
+	}
 	for elem := range *set {
 		if !other.Contains(elem) {
 			return false