refactor: improved Dockerfile (#672)

Author: adriang-90

Dockerfile

@@ -1,13 +1,16 @@
-FROM golang:bullseye as builder
+FROM --platform=${BUILDPLATFORM} golang:bullseye as builder
 
 WORKDIR /build
-COPY go.mod go.sum ./
-RUN go mod download
 COPY . . 
-RUN CGO_ENABLED=0 go build -a -o trufflehog main.go
+ENV CGO_ENABLED=0
+ARG TARGETOS TARGETARCH
+RUN  --mount=type=cache,target=/go/pkg/mod \
+     --mount=type=cache,target=/root/.cache/go-build \
+     GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -o trufflehog .
 
 FROM alpine:3.15
 RUN apk add --no-cache git
 COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
 COPY --from=builder /build/trufflehog /usr/bin/trufflehog
 ENTRYPOINT ["/usr/bin/trufflehog"]
+