Ilegal http header

[ivanalexo]

Hi there,

I'm trying to pass a variable through headers: for example:
let headers = {'x-apikey': apiKey }
but when I run it, the log says that the apiKey value is an ilegal http header this variable (apiKey) return a random string code, but when I pasted the code instead of the variable it runs.
I want to know how pass the variable.