build(deps): update golang docker tag to v1.21.6 (#52)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Dockerfile

@@ -1,5 +1,5 @@
 # Build the application from source.
-FROM golang:1.21.5-alpine@sha256:4db4aac30880b978cae5445dd4a706215249ad4f43d28bd7cdf7906e9be8dd6b AS go-builder
+FROM golang:1.21.6-alpine@sha256:fd78f2fb1e49bcf343079bbbb851c936a18fc694df993cbddaa24ace0cc724c5 AS go-builder
 
 WORKDIR /app
 COPY go.mod go.sum cmd ./