Sent payloads not valid JSON, wrapped in function call

[grandstairs]

When I send a message it shows up in cloudwatch as a function call for some reason.

f, _ := fluent.New(fluent.Config{FluentPort: port, FluentHost: "localhost"})
f.Post("tag_name_here", msg) // msg is EMF payload
f.Close()

I am trying to use fluent bit to post EMF payloads to a specific cloudwatch log group so I can use them for metrics.

My fluentbit configuration if it helps

[SERVICE]
    HTTP_Server  On
    HTTP_Listen  0.0.0.0
    HTTP_PORT    2020
    Flush        1
    Grace        30
    Log_Level    info
    storage.path /var/log/flb-storage/
    storage.max_chunks_up  32

[INPUT]
    Name          tcp
    Alias         TCP-ServiceMetrics
    Tag           ServiceMetrics
    Listen        0.0.0.0
    Port          5172
    Format        none
    Chunk_Size    32
    Buffer_Size   256
    storage.type  filesystem

[OUTPUT]
    Name                cloudwatch_logs
    Alias               CloudWatch-ServiceMetrics
    Match               ServiceMetrics
    region              ${LOG_REGION}
    log_group_name      SampleApp-${STAGE}-ServiceMetrics
    log_stream_prefix   ServiceMetrics-${HOSTNAME}
    log_key             log
    log_format          json/emf
    auto_create_group   false
    retry_limit         3
    endpoint            ${CLOUDWATCH_ENDPOINT}