Add concurrency for main.yml

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 39bcd08e484cca973f8f67feda7e63e872e2f476..cfbcbd778143aa9cd2967683d798e5d04fde0fa2 100644 (file)
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -2,6 +2,10 @@ name: CI
 
 on: [push, pull_request]
 
+concurrency:
+  group: ${{ github.event_name }}-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{github.event_name == 'pull_request'}}
+
 jobs:
   ubuntu18-minimal:
     name: ubuntu 18.04 minimal