PEM_read_bio_PrivateKey returns NULL

Question

I have a JSON file containing the private key (downloaded it from Google Developer Console for Service Accounts). For building JWT, when I try to load the private key as a EVP_PKEY structure using PEM_read_bio_PrivateKey(), it returns NULL (an error).

Code

const char *private_key = 
   json_object_get_string(json_object_object_get(token_file_obj, 
                                                   "private_key"));
printf("Private key --> [%s]\n", private_key);

/* Not sure whether this is needed, just added all three in case needed X-D */
OpenSSL_add_all_algorithms();
OpenSSL_add_all_ciphers();
OpenSSL_add_all_digests();

BIO *bio = BIO_new_mem_buf(private_key, (int) sizeof(private_key));
if (bio == NULL) {
    printf("Bio is null **** \n");
    return FAILED_OPERATION;
}

EVP_PKEY *pkey = PEM_read_bio_PrivateKey(bio, NULL, 0, NULL);
if (pkey == NULL) {
    printf("Failed operation error code %d\n", errno);
    return FAILED_OPERATION;
}

Output

Note: I've changed the Private Key copied from Output.

Private key --> [-----BEGIN PRIVATE KEY-----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-----END PRIVATE KEY-----
]
Failed operation error code 0

Things I have tried

1. Replaced the \n in the private key from JSON file with newline, and compared it with the private key printed using printf(). Both had the same checksum.
2. Removed the -----BEGIN PRIVATE KEY----- and -----END PRIVATE KEY----- from the private key and tried - Did not work.