Fix usage of pub (#258)

.github/workflows/ci.yml

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index e9ec5a5..cfbf442 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -33,9 +33,9 @@
 
       - run: dart test --coverage coverage
         if: matrix.sdk == 'dev' && steps.install.outcome == 'success'
-      - run: pub global activate coverage
+      - run: dart pub global activate coverage
         if: matrix.sdk == 'dev'
-      - run: pub global run coverage:format_coverage --packages=.packages -i coverage --report-on=lib --lcov > coverage/lcov.info
+      - run: dart pub global run coverage:format_coverage --packages=.packages -i coverage --report-on=lib --lcov > coverage/lcov.info
         if: matrix.sdk == 'dev'
       - uses: coverallsapp/github-action@master
         with: