Fix build with go 1.11

.github/workflows/test-package.yml

@@ -14,6 +14,8 @@ jobs:
  matrix:
  os: [ubuntu-20.04, windows-latest]
  go-version: ['1.11', '1.12', '1.13', '1.14', '1.15', '1.16', '1.17', '1.18', '1.19', '1.20', '1.21', '1.22']
+ env:
+ GO111MODULE: on
 
  steps:
  - uses: actions/checkout@v2

Makefile

@@ -1,6 +1,6 @@
 TEST?=./...
 
-export GO111MODULE=auto
+export GO111MODULE=on
 
 default: alldeps test
 

features/fixtures/app/Dockerfile

@@ -11,6 +11,9 @@ WORKDIR /app/src/github.com/bugsnag/bugsnag-go/v2
 # Ensure subsequent steps are re-run if the GO_VERSION variable changes
 ARG GO_VERSION
 
+# Required for go 1.11 as modules are not enabled by default
+ENV GO111MODULE="on"
+
 # Get bugsnag dependencies using a conditional call to run go get or go install based on the go version
 RUN if [[ $(echo -e "1.11\n$GO_VERSION\n1.16" | sort -V | head -2 | tail -1) == "$GO_VERSION" ]]; then \
  echo "Version is between 1.11 and 1.16, running go get"; \

features/fixtures/autoconfigure/Dockerfile

@@ -11,6 +11,9 @@ WORKDIR /app/src/github.com/bugsnag/bugsnag-go/v2
 # Ensure subsequent steps are re-run if the GO_VERSION variable changes
 ARG GO_VERSION
 
+# Required for go 1.11 as modules are not enabled by default
+ENV GO111MODULE="on"
+
 # Get bugsnag dependencies using a conditional call to run go get or go install based on the go version
 RUN if [[ $(echo -e "1.11\n$GO_VERSION\n1.16" | sort -V | head -2 | tail -1) == "$GO_VERSION" ]]; then \
  echo "Version is between 1.11 and 1.16, running go get"; \

features/fixtures/net_http/Dockerfile

@@ -13,6 +13,9 @@ WORKDIR /app/src/github.com/bugsnag/bugsnag-go/v2
 # Ensure subsequent steps are re-run if the GO_VERSION variable changes
 ARG GO_VERSION
 
+# Required for go 1.11 as modules are not enabled by default
+ENV GO111MODULE="on"
+
 # Get bugsnag dependencies using a conditional call to run go get or go install based on the go version
 RUN if [[ $(echo -e "1.11\n$GO_VERSION\n1.16" | sort -V | head -2 | tail -1) == "$GO_VERSION" ]]; then \
  echo "Version is between 1.11 and 1.16, running go get"; \