Update README.md

Author: davidbuzinski

README.md

@@ -31,7 +31,21 @@ steps:
     inputs:
       sourceFolder: source
       codeCoverageCobertura: coverage.xml
-  - script: bash <(curl -s https://codecov.io/bash)
+  - script: |
+      # download Codecov CLI
+      curl -Os https://cli.codecov.io/latest/linux/codecov
+      
+      # integrity check
+      curl https://keybase.io/codecovsecurity/pgp_keys.asc | gpg --no-default-keyring --keyring trustedkeys.gpg --import # One-time step  
+      curl -Os https://cli.codecov.io/latest/linux/codecov
+      curl -Os https://cli.codecov.io/latest/linux/codecov.SHA256SUM
+      curl -Os https://cli.codecov.io/latest/linux/codecov.SHA256SUM.sig
+      gpgv codecov.SHA256SUM.sig codecov.SHA256SUM
+
+      # upload to Codecov 
+      shasum -a 256 -c codecov.SHA256SUM
+      sudo chmod +x codecov
+      ./codecov upload-process -t $(CODECOV_TOKEN)
 ```
 
 ### CircleCI