Extend process.env in TypeScript

Create a .d.ts file somewhere (e.g., src/types/env.d.ts) and make sure this is included in the typeRoots setting in your tsconfig.json.

Example typeRoots value in tsconfig.json:

 "typeRoots": [
    "./node_modules/@types",
    "./src/types"
 ],

Then extend the NodeJS.ProcessEnv interface in your .d.ts file:

declare namespace NodeJS {
  export interface ProcessEnv {
    FOO: string
    BAR: string
  }
}

Now, you can write something like process.env.FOO without any TypeScript errors.