Elasticsearch - Accessing nested variables

I would like to get coordinates from my data.

"userLoc" : {
    "locNm" : "Alexandra Road",
    "coordinates" : [ 
        103.8174926, 
        1.29143
    ],

I tried the following to get the second value of coordinates but it didn't work out.

"script": "return _score*doc['userLoc'].coordinates[1];"

Got following error.

{
   "error": "SearchPhaseExecutionException[Failed to execute phase [query], all shards failed; shardFailures {[H94j5eYQRXantctqOKMduw][merchantindex][0]: QueryPhaseExecutionException[[merchantindex][0]: query[function score (_all:test,function=script[return _score*doc['userLoc'].coordinates[1];], params [null])],from[0],size[10]: Query Failed [Failed to execute main query]]; nested: GroovyScriptExecutionException[ElasticsearchIllegalArgumentException[No field found for [userLoc] in mapping with types []]]; }{[H94j5eYQRXantctqOKMduw][merchantindex][1]: QueryPhaseExecutionException[[merchantindex][1]: query[function score (_all:test,function=script[return _score*doc['userLoc'].coordinates[1];], params [null])],from[0],size[10]: Query Failed [Failed to execute main query]]; nested: GroovyScriptExecutionException[ElasticsearchIllegalArgumentException[No field found for [userLoc] in mapping with types []]]; }{[H94j5eYQRXantctqOKMduw][merchantindex][2]: QueryPhaseExecutionException[[merchantindex][2]: query[function score (_all:test,function=script[return _score*doc['userLoc'].coordinates[1];], params [null])],from[0],size[10]: Query Failed [Failed to execute main query]]; nested: GroovyScriptExecutionException[ElasticsearchIllegalArgumentException[No field found for [userLoc] in mapping with types []]]; }{[H94j5eYQRXantctqOKMduw][merchantindex][3]: QueryPhaseExecutionException[[merchantindex][3]: query[function score (_all:test,function=script[return _score*doc['userLoc'].coordinates[1];], params [null])],from[0],size[10]: Query Failed [Failed to execute main query]]; nested: GroovyScriptExecutionException[ElasticsearchIllegalArgumentException[No field found for [userLoc] in mapping with types []]]; }{[H94j5eYQRXantctqOKMduw][merchantindex][4]: QueryPhaseExecutionException[[merchantindex][4]: query[function score (_all:test,function=script[return _score*doc['userLoc'].coordinates[1];], params [null])],from[0],size[10]: Query Failed [Failed to execute main query]]; nested: GroovyScriptExecutionException[ElasticsearchIllegalArgumentException[No field found for [userLoc] in mapping with types []]]; }]",
   "status": 500
}