Update Docker image to go1.15-cuda10.2

.gitlab-ci.yml

@@ -9,7 +9,7 @@ cache:
 variables:
   REPO_DIR: gitlab.com/elixxir
   REPO_NAME: primitives
-  DOCKER_IMAGE: elixxirlabs/cuda-go:latest
+  DOCKER_IMAGE: elixxirlabs/cuda-go:go1.15-cuda10.2
   MIN_CODE_COVERAGE: "89.0"
 
 before_script:

go.mod

 module gitlab.com/xx_network/primitives
 
+go 1.15
+
 require (
 	github.com/pkg/errors v0.9.1
 	github.com/spf13/jwalterweatherman v1.1.0