Update base image version to fix sec vuln and renamed Dockerfiles for clarity

docker/Dockerfile.linux.amd64

@@ -1,11 +1,11 @@
-FROM golang:1.22.1-alpine as builder
+FROM golang:1.22.7-alpine as builder
 
 WORKDIR /go/src/drone-email
 COPY . .
 
 RUN GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build
 
-FROM alpine:3.14
+FROM alpine:3.20
 
 RUN apk add --no-cache ca-certificates tzdata
 

docker/Dockerfile.linux.arm64

@@ -1,11 +1,11 @@
-FROM golang:1.22.1-alpine as builder
+FROM golang:1.22.7-alpine as builder
 
 WORKDIR /go/src/drone-email
 COPY . .
 
 RUN GOOS=linux GOARCH=arm GOARM=7 CGO_ENABLED=0 go build
 
-FROM alpine:3.14
+FROM alpine:3.20
 
 RUN apk add --no-cache ca-certificates tzdata
 

go.mod

@@ -1,3 +1,3 @@
 module github.com/drone-plugins/drone-email
 
-go 1.22.1
+go 1.22.7