diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5815086..ea534c2 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -8,13 +8,16 @@ on:
       - '*.*'
   pull_request:
 
+env:
+  GO111MODULE: on
+
 jobs:
   tests:
     name: Tests
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go-version: ['1.8', '1.9', '1.10', '1.11', '1.12', '1.13', '1.14']
+        go-version: ['1.8', '1.9', '1.10', '1.11', '1.12', '1.13', '1.14', '1.15']
     steps:
       - name: Set up Go ${{ matrix.go-version }}
         uses: actions/setup-go@v2