Align go.mod version with Kubernetes (Go 1.20)

Signed-off-by: Stefan Prodan <stefan.prodan@gmail.com>

Author: stefanprodan

api/go.mod

@@ -1,6 +1,6 @@
 module github.com/fluxcd/helm-controller/api
 
-go 1.18
+go 1.20
 
 require (
 	github.com/fluxcd/pkg/apis/kustomize v1.1.0

go.mod

@@ -1,6 +1,6 @@
 module github.com/fluxcd/helm-controller
 
-go 1.18
+go 1.20
 
 replace github.com/fluxcd/helm-controller/api => ./api
 

tests/fuzz/Dockerfile.builder

@@ -1,5 +1,11 @@
 FROM gcr.io/oss-fuzz-base/base-builder-go
 
+RUN wget https://go.dev/dl/go1.20.5.linux-amd64.tar.gz \
+    && mkdir temp-go \
+    && rm -rf /root/.go/* \
+    && tar -C temp-go/ -xzf go1.20.5.linux-amd64.tar.gz \
+    && mv temp-go/go/* /root/.go/
+
 ENV SRC=$GOPATH/src/github.com/fluxcd/helm-controller
 ENV FLUX_CI=true