fix(docker): bump alpine / go

Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.13.1 AS builder
+FROM golang:1.16-alpine AS builder
 RUN apk add -U --no-cache \
   build-base \
   ca-certificates \
@@ -14,7 +14,7 @@ RUN go mod download
 COPY . .
 RUN GOOS=linux go build -o gonic cmd/gonic/gonic.go
 
-FROM alpine:3.13.1
+FROM alpine:3.13.5
 LABEL org.opencontainers.image.source https://github.com/sentriz/gonic
 RUN apk add -U --no-cache \
   ffmpeg \

Dockerfile.debug

@@ -1,5 +1,3 @@
-# syntax=docker/dockerfile:experimental
-
 FROM golang:1.16-alpine AS builder
 RUN apk add -U --no-cache \
     build-base \

Dockerfile.dev

@@ -14,7 +14,7 @@ RUN --mount=type=cache,target=/go/pkg/mod \
   --mount=type=cache,target=/root/.cache/go-build \
   GOOS=linux go build -o gonic cmd/gonic/gonic.go
 
-FROM alpine:3.12.3
+FROM alpine:3.13.5
 RUN apk add -U --no-cache \
   ffmpeg \
   ca-certificates