Revert "Drop support for Go 1.11."

This reverts commit 12fde525c7.

.travis.yml

@@ -3,18 +3,18 @@ sudo: false
 
 matrix:
   include:
+    - go: "1.9"
+    - go: "1.10"
+    - go: "1.11"
+      env:
+      - GO111MODULE=off
+      - VET=1
+    - go: "1.11"
+      env: GO111MODULE=on
     - go: "1.12"
       env: GO111MODULE=off
     - go: "1.12"
       env: GO111MODULE=on
-    - go: "1.13"
-      env: GO111MODULE=off
-    - go: "1.13"
-      env: GO111MODULE=on
-    - go: "1.14"
-      env: GO111MODULE=off
-    - go: "1.14"
-      env: GO111MODULE=on
     - go: tip
 
 script:

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.13.8-alpine as builder
+FROM golang:1.11.10-alpine as builder
 MAINTAINER FullStory Engineering
 
 # currently, a module build requires gcc (so Go tool can build
@@ -17,6 +17,7 @@ COPY cmd /tmp/fullstorydev/grpcurl/cmd
 ENV CGO_ENABLED=0
 ENV GOOS=linux
 ENV GOARCH=amd64
+ENV GO111MODULE=on
 RUN go build -o /grpcurl \
     -ldflags "-w -extldflags \"-static\" -X \"main.version=$(cat VERSION)\"" \
     ./cmd/grpcurl

go.mod

@@ -1,6 +1,6 @@
 module github.com/fullstorydev/grpcurl
 
-go 1.13
+go 1.14
 
 require (
 	github.com/golang/protobuf v1.3.3