fix travis pipelines

.travis.yml

@@ -1,17 +1,15 @@
 language: go
 
 go:
-  - "1.5.x"
-  - "1.6.x"
-  - "1.7.x"
-  - "1.8.x"
-  - "1.9.x"
-  - "1.10.x"
   - "1.11.x"
+  - "1.12.x"
+  - "1.13.x"
+  - "1.14.x"
+  - "1.15.x"
 
 script:
-  - go vet github.com/jfilipczyk/gomatch
-  - go test -v -race -coverprofile=coverage.txt -covermode=atomic
+  - env GO111MODULE=on go vet github.com/jfilipczyk/gomatch
+  - env GO111MODULE=on go test -v -race -coverprofile=coverage.txt -covermode=atomic
 
 after_success:
   - bash <(curl -s https://codecov.io/bash)

go.mod

@@ -3,8 +3,7 @@ module github.com/jfilipczyk/gomatch
 go 1.15
 
 require (
-	github.com/davecgh/go-spew v1.1.1
+	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/google/uuid v1.1.0
-	github.com/pmezard/go-difflib v1.0.0
 	github.com/stretchr/testify v1.3.0
 )