fix: moves gcov2lcov download earlier to take advantage of caching

Dockerfile.test

@@ -4,16 +4,16 @@ FROM 274295908850.dkr.ecr.eu-west-1.amazonaws.com/i/golang:1.21.1-alpine3.18
 # Switch to generic build directory
 WORKDIR /usr/src/service
 
+# Install and run the gocov2lcov adapter module
+RUN go install github.com/jandelgado/[email protected]
+
 # Download and verify dependencies
 COPY go.mod go.sum ./
 RUN go mod download && go mod verify
 
 # Copy in source files
 COPY main.go main_test.go ./
 
-# Install and run the gocov2lcov adapter module
-RUN go install github.com/jandelgado/[email protected]
-
 # By default, coverage is outputted in the same directory
 ENV COVERAGE_DIRECTORY "."