You can use node to generate JWT key which further can be used for JWT authentication.
In the terminal, on the machine where node is installed, run the following command:
node -e "console.log(require('crypto').randomBytes(256).toString('base64'));"
The output will be like this:
8YlxFlrb1vDa/7pNaTkbuvNWLMfWZQ7bgrV3IU0nLulff2O536gQWkLdMbfDBOYLedB2QzsGQEuUTxWv79kVmiGgRBHN22vYId+g8O9g0kD+EI7TF/Lc66hAnrQ5wsPEwRSF0q3j3Bs9yEUAvxaXjkNEci4bqh8MG/fBzYT/w/x0ZDt56I3uCM8JKa90kaTbexDYynoVGbd6QJHVmpb0Zh6P2pWaC4nwBVnDRMmdmvRxPD1CgyczXnWXQvSr3ydXhe29n3ZNpFUSeD3vHTZPzkovQcMUAsG1N0Gq6zy0uPoc96foWBLvUhgBpubi1MwZqTiMC7UKGj2+vPOCMsMlIA==
You can use the generated key for your JWT authentication logic.