Not able to read TOML file using Go with BurntSushi library

I am using the BurntSushi library to load a TOML configuration file in my GO application. I have followed the instructions on the library to write the structs and the configuration toml file itself. I am running into some trouble, and I cant seem to find the source of my issues.

Here are the details:

Structs:

package main
//ConfigurationParameters provides the struct to hold configuration parameters from config file
type ConfigurationParameters struct {
Title string
//serviceDiscovery captures configuration parameters needed for service discovery registration with Consul
ServiceDiscovery ConsulConf `toml:"ServiceDiscovery"`
//metadataReporting captures which metadata to be registered with service into consul for use during discovery
MetadataReporting MetaDataConf `toml:"MetadataReporting"`
//awsTagsToLabels captures the aws tags that should be added to reported metrics as Labels
AwsTagsToLabels LabelConf `toml:"AwsTagsToLabels"`
//collectors captures the list of collectors to use
Collectors CollectorConf `toml:"Collectors"`
//service captures agent related configurations
Service ServiceConf `toml:"Service"`
}
//ConsulConf captures configuration parameters needed for service discovery registration with Consul
type ConsulConf struct {
enabled    bool
endpoint   string
port       int
datacenter string
serviceID  string
}
//MetaDataConf captures which metadata to be registered with service into consul for use during discovery
type MetaDataConf struct {
enabled   bool
awsregion string
}
//LabelConf captures the aws tags that should be added to reported metrics as Labels
type LabelConf struct {
enabled       bool
refreshPeriod int
}
//CollectorConf captures the list of collectors to use
type CollectorConf struct {
goCollectionEnabled       bool
exporterCollectionEnabled bool
wmiCollectionEnabled      bool
agentCollectionEnabled    bool
enabledCollectors         string
metricMap                 []MetricMap
}
//MetricMap captures a mapping between one or more WMI metrics and the name it should be reported with
type MetricMap struct {
wmiMetricName  []string
exportName     string
dropMetric     bool
computedMetric bool
computeLogic   string
}
//ServiceConf captures agent related configurations
type ServiceConf struct {
listenIP           string
listenPort         int
metricPath         string
collectionInterval int
serviceName        string
}

and the configuration toml file:

Title = "WMI Exporter Configuration"
[ServiceDiscovery]
enabled = true
endpoint = "my.consul.server"
port = 5500
datacenter = "ucm-west"
serviceID = "ucm.agent.wmiExporter"
[MetadataReporting]
enabled = true
awsregion = "us-west-2"
[AwsTagsToLabels]
enabled = true
refreshPeriod = 3600
[Collectors]
goCollectionEnabled = true
exporterCollectionEnabled = true
wmiCollectionEnabled = true
agentCollectionEnabled = false
enabledCollectors   = "cpu,os"
[Collectors.MetricMap.0]
wmiMetricName = ["test"]
exportName = "export_test"
[Service]
listenPort =  9103
metricPath = "/metrics"
collectionInterval = 60
serviceName = "wmi_exporter"

And the code that reads the config file:

// InitializeFromConfig reads configuration parameters from configuration file and initializes this service
func InitializeFromConfig(configfile string) ConfigurationParameters {
conf := ConfigurationParameters{}
if configfile == "" {
return conf
}
_, err := toml.DecodeFile(configfile, &conf)
if err != nil {
log.Fatalf("Cannot parse configuration file at %s. Error=%s", configfile, err)
}
//at this point, conf is a fully loaded configuration now; now initialize everything from conf
return conf
}

The issue I am facing is that only the value for the Title attribute gets mapped into the GO struct members. All of the other configs stay unmapped. Looking at all of the examples on github for BurntSushi and https://stackoverflow.com/questions/34307488/go-how-to-use-toml-files, I cant see any difference from what I am currently doing in code.

I also used the tomlv validator from the BurntSushi package to look at the types from the TOML file, and I believe they look correct.

Datatypes:

Title                                             String
ServiceDiscovery                                  Hash
ServiceDiscovery.enabled                      Bool
ServiceDiscovery.endpoint                     String
ServiceDiscovery.port                         Integer
ServiceDiscovery.datacenter                   String
ServiceDiscovery.serviceID                    String
MetadataReporting                                 Hash
MetadataReporting.enabled                     Bool
MetadataReporting.awsregion                   String
AwsTagsToLabels                                   Hash
AwsTagsToLabels.enabled                       Bool
AwsTagsToLabels.refreshPeriod                 Integer
Collectors                                        Hash
Collectors.goCollectionEnabled                Bool
Collectors.exporterCollectionEnabled          Bool
Collectors.wmiCollectionEnabled               Bool
Collectors.agentCollectionEnabled             Bool
Collectors.enabledCollectors                  String
Collectors.MetricMap.0                    Hash
Collectors.MetricMap.0.wmiMetricName  Array
Collectors.MetricMap.0.exportName     String
Service                                           Hash
Service.listenPort                            Integer
Service.metricPath                            String
Service.collectionInterval                    Integer
Service.serviceName                           String

I tried debugging into the BurntSushi package code, but it was not very helpful (the Delve debugger was not able to display some of the variables in that package, and seemed to randomly jump between the lines in that package).

Any help or pointers on what I could be doing wrong?

Thanks.

You need to export any fields that you want BurntSushi/toml to unmarshal into, including subfields:

//ConfigurationParameters provides the struct to hold configuration parameters from config file
type ConfigurationParameters struct {
Title string
//serviceDiscovery captures configuration parameters needed for service discovery registration with Consul
ServiceDiscovery ConsulConf `toml:"ServiceDiscovery"`
//metadataReporting captures which metadata to be registered with service into consul for use during discovery
MetadataReporting MetaDataConf `toml:"MetadataReporting"`
//awsTagsToLabels captures the aws tags that should be added to reported metrics as Labels
AwsTagsToLabels LabelConf `toml:"AwsTagsToLabels"`
//collectors captures the list of collectors to use
Collectors CollectorConf `toml:"Collectors"`
//service captures agent related configurations
Service ServiceConf `toml:"Service"`
}
//ConsulConf captures configuration parameters needed for service discovery registration with Consul
type ConsulConf struct {
Enabled    bool
Endpoint   string
Port       int
Datacenter string
ServiceID  string
}
//MetaDataConf captures which metadata to be registered with service into consul for use during discovery
type MetaDataConf struct {
Enabled   bool
Awsregion string
}
//LabelConf captures the aws tags that should be added to reported metrics as Labels
type LabelConf struct {
Enabled       bool
RefreshPeriod int
}
//CollectorConf captures the list of collectors to use
type CollectorConf struct {
GoCollectionEnabled       bool
ExporterCollectionEnabled bool
WmiCollectionEnabled      bool
AgentCollectionEnabled    bool
EnabledCollectors         string
MetricMap                 []MetricMap
}
//MetricMap captures a mapping between one or more WMI metrics and the name it should be reported with
type MetricMap struct {
WmiMetricName  []string
ExportName     string
DropMetric     bool
ComputedMetric bool
ComputeLogic   string
}
//ServiceConf captures agent related configurations
type ServiceConf struct {
ListenIP           string
ListenPort         int
MetricPath         string
CollectionInterval int
ServiceName        string
}

Also i'm not sure what this Collectors.MetricMap.0 syntax is supposed to represent but to unmarshal your toml values into the []MetricMap field
what you want to do is something like this instead:

[[Collectors.MetricMap]]
wmiMetricName = ["test"]
exportName = "export_test"