fix(dockerfile): use latest supported packages for golang v1.18

Author: HarryVasanth

Dockerfile

@@ -3,12 +3,14 @@ FROM golang:1.18-alpine
 ENV GIT_TERMINAL_PROMPT=0
 RUN apk add --no-cache git
 
-RUN go install github.com/mvdan/gofumpt@latest
+# Install gofumpt (latest v0.4.0 to support go1.18)
+RUN go install mvdan.cc/gofumpt@v0.4.0
 RUN go install github.com/01-edu/rc@latest
 
 WORKDIR /piscine-go
 RUN go mod init piscine-go
-RUN go get github.com/01-edu/z01@latest
+# Install z01 package (latest v0.2.0, same as go.mod)
+RUN go get github.com/01-edu/z01@v0.2.0
 
 WORKDIR /go-tests
 COPY go.* ./