kubernetes: how to link secret tls crt/key with files or configMap?

Is there a way to link secret tls crt/key with files?

apiVersion: v1
kind: Secret
metadata:
  name: hello-app-tls
  namespace: dev
type: kubernetes.io/tls
data:
  tls.crt: <crt_filePath>
  tls.key: <key_filePath>

Or reference values from a ConfigMap like:

apiVersion: v1
kind: Secret
metadata:
  name: hello-app-tls
  namespace: dev
type: kubernetes.io/tls
data:
  tls.crt:
    valueFrom:
       configMapKeyRef:
         name: configmap_tls
         key: crt
  tls.key:
    valueFrom:
       configMapKeyRef:
         name: configmap_tls
         key: key

Error:

Secret in version "v1" cannot be handled as a Secret: json: cannot unmarshal object into Go struct field Secret.data of type []uint8

That cryptic error about unmarshalling string to a map of string means that the module was unable to resolve the content of values parameter to the contents of the actual file. Which caused the issue.

In your secret you can't give data directly. You have to encode your data in base64 format.

As mentioned in the github link by @ MadEngineX, try running the below command at data field:

tls.crt: {{ .Files.Get "api-gateway/google/files/tls.crt" | b64enc | quote  }}

Or

tls.crt: {{ .Files.Get "api-gateway/google/files/tls.crt" | toString | b64enc | quote   }}

Example-

apiVersion: v1
kind: Secret
metadata:
  name: hello-app-tls
  namespace: dev
type: kubernetes.io/tls
data:
  tls.crt: {{ .Files.Get "api-gateway/google/files/tls.crt" | b64enc | quote  }}