func (im *IndexMapping) UnmarshalJSON(data []byte) error {
	var tmp map[string]json.RawMessage
	err := json.Unmarshal(data, &tmp)
	if err != nil {
		return err
	}
	im.cache = registry.NewCache()
	im.CustomAnalysis = newCustomAnalysis()
	im.TypeField = defaultTypeField
	im.DefaultType = defaultType
	im.DefaultAnalyzer = defaultAnalyzer
	im.DefaultDateTimeParser = defaultDateTimeParser
	im.DefaultField = defaultField
	im.DefaultMapping = NewDocumentMapping()
	im.TypeMapping = make(map[string]*DocumentMapping)
	im.StoreDynamic = StoreDynamic
	im.IndexDynamic = IndexDynamic
	var invalidKeys []string
	for k, v := range tmp {
		switch k {
		case "analysis":
			err := json.Unmarshal(v, &im.CustomAnalysis)
			if err != nil {
				return err
			}
		case "type_field":
			err := json.Unmarshal(v, &im.TypeField)
			if err != nil {
				return err
			}
		case "default_type":
			err := json.Unmarshal(v, &im.DefaultType)
			if err != nil {
				return err
			}
		case "default_analyzer":
			err := json.Unmarshal(v, &im.DefaultAnalyzer)
			if err != nil {
				return err
			}
		case "default_datetime_parser":
			err := json.Unmarshal(v, &im.DefaultDateTimeParser)
			if err != nil {
				return err
			}
		case "default_field":
			err := json.Unmarshal(v, &im.DefaultField)
			if err != nil {
				return err
			}
		case "default_mapping":
			err := json.Unmarshal(v, &im.DefaultMapping)
			if err != nil {
				return err
			}
		case "types":
			err := json.Unmarshal(v, &im.TypeMapping)
			if err != nil {
				return err
			}
		case "store_dynamic":
			err := json.Unmarshal(v, &im.StoreDynamic)
			if err != nil {
				return err
			}
		case "index_dynamic":
			err := json.Unmarshal(v, &im.IndexDynamic)
			if err != nil {
				return err
			}
		default:
			invalidKeys = append(invalidKeys, k)
		}
	}
	if MappingJSONStrict && len(invalidKeys) > 0 {
		return fmt.Errorf("index mapping contains invalid keys: %v", invalidKeys)
	}
	err = im.CustomAnalysis.registerAll(im)
	if err != nil {
		return err
	}
	return nil
}
UnmarshalJSON offers custom unmarshaling with optional strict validation
package bleve
import (
	"encoding/json"
	"fmt"
	"github.com/blevesearch/bleve/analysis"
	"github.com/blevesearch/bleve/analysis/analyzers/standard_analyzer"
	"github.com/blevesearch/bleve/analysis/datetime_parsers/datetime_optional"
	"github.com/blevesearch/bleve/document"
	"github.com/blevesearch/bleve/registry"
)
var MappingJSONStrict = false
const defaultTypeField = "_type"
const defaultType = "_default"
const defaultField = "_all"
const defaultAnalyzer = standard_analyzer.Name
const defaultDateTimeParser = datetime_optional.Name
type customAnalysis struct {
	CharFilters     map[string]map[string]interface{} `json:"char_filters,omitempty"`
	Tokenizers      map[string]map[string]interface{} `json:"tokenizers,omitempty"`
	TokenMaps       map[string]map[string]interface{} `json:"token_maps,omitempty"`
	TokenFilters    map[string]map[string]interface{} `json:"token_filters,omitempty"`
	Analyzers       map[string]map[string]interface{} `json:"analyzers,omitempty"`
	DateTimeParsers map[string]map[string]interface{} `json:"date_time_parsers,omitempty"`
}
func (c *customAnalysis) registerAll(i *IndexMapping) error {
	for name, config := range c.CharFilters {
		_, err := i.cache.DefineCharFilter(name, config)
		if err != nil {
			return err
		}
	}
	if len(c.Tokenizers) > 0 {
		todo := map[string]struct{}{}
		for name := range c.Tokenizers {
			todo[name] = struct{}{}
		}
		registered := 1
		errs := []error{}
		for len(todo) > 0 && registered > 0 {
			registered = 0
			errs = []error{}
			for name := range todo {
				config := c.Tokenizers[name]
				_, err := i.cache.DefineTokenizer(name, config)
				if err != nil {
					errs = append(errs, err)
				} else {
					delete(todo, name)
					registered++
				}
			}
		}
		if len(errs) > 0 {
			return errs[0]
		}
	}
	for name, config := range c.TokenMaps {
		_, err := i.cache.DefineTokenMap(name, config)
		if err != nil {
			return err
		}
	}
	for name, config := range c.TokenFilters {
		_, err := i.cache.DefineTokenFilter(name, config)
		if err != nil {
			return err
		}
	}
	for name, config := range c.Analyzers {
		_, err := i.cache.DefineAnalyzer(name, config)
		if err != nil {
			return err
		}
	}
	for name, config := range c.DateTimeParsers {
		_, err := i.cache.DefineDateTimeParser(name, config)
		if err != nil {
			return err
		}
	}
	return nil
}
func newCustomAnalysis() *customAnalysis {
	rv := customAnalysis{
		CharFilters:     make(map[string]map[string]interface{}),
		Tokenizers:      make(map[string]map[string]interface{}),
		TokenMaps:       make(map[string]map[string]interface{}),
		TokenFilters:    make(map[string]map[string]interface{}),
		Analyzers:       make(map[string]map[string]interface{}),
		DateTimeParsers: make(map[string]map[string]interface{}),
	}
	return &rv
}
type IndexMapping struct {
	TypeMapping           map[string]*DocumentMapping `json:"types,omitempty"`
	DefaultMapping        *DocumentMapping            `json:"default_mapping"`
	TypeField             string                      `json:"type_field"`
	DefaultType           string                      `json:"default_type"`
	DefaultAnalyzer       string                      `json:"default_analyzer"`
	DefaultDateTimeParser string                      `json:"default_datetime_parser"`
	DefaultField          string                      `json:"default_field"`
	StoreDynamic          bool                        `json:"store_dynamic"`
	IndexDynamic          bool                        `json:"index_dynamic"`
	CustomAnalysis        *customAnalysis             `json:"analysis,omitempty"`
	cache                 *registry.Cache
}
func (im *IndexMapping) AddCustomCharFilter(name string, config map[string]interface{}) error {
	_, err := im.cache.DefineCharFilter(name, config)
	if err != nil {
		return err
	}
	im.CustomAnalysis.CharFilters[name] = config
	return nil
}
func (im *IndexMapping) AddCustomTokenizer(name string, config map[string]interface{}) error {
	_, err := im.cache.DefineTokenizer(name, config)
	if err != nil {
		return err
	}
	im.CustomAnalysis.Tokenizers[name] = config
	return nil
}
func (im *IndexMapping) AddCustomTokenMap(name string, config map[string]interface{}) error {
	_, err := im.cache.DefineTokenMap(name, config)
	if err != nil {
		return err
	}
	im.CustomAnalysis.TokenMaps[name] = config
	return nil
}
func (im *IndexMapping) AddCustomTokenFilter(name string, config map[string]interface{}) error {
	_, err := im.cache.DefineTokenFilter(name, config)
	if err != nil {
		return err
	}
	im.CustomAnalysis.TokenFilters[name] = config
	return nil
}
func (im *IndexMapping) AddCustomAnalyzer(name string, config map[string]interface{}) error {
	_, err := im.cache.DefineAnalyzer(name, config)
	if err != nil {
		return err
	}
	im.CustomAnalysis.Analyzers[name] = config
	return nil
}
func (im *IndexMapping) AddCustomDateTimeParser(name string, config map[string]interface{}) error {
	_, err := im.cache.DefineDateTimeParser(name, config)
	if err != nil {
		return err
	}
	im.CustomAnalysis.DateTimeParsers[name] = config
	return nil
}
func NewIndexMapping() *IndexMapping {
	return &IndexMapping{
		TypeMapping:           make(map[string]*DocumentMapping),
		DefaultMapping:        NewDocumentMapping(),
		TypeField:             defaultTypeField,
		DefaultType:           defaultType,
		DefaultAnalyzer:       defaultAnalyzer,
		DefaultDateTimeParser: defaultDateTimeParser,
		DefaultField:          defaultField,
		IndexDynamic:          IndexDynamic,
		StoreDynamic:          StoreDynamic,
		CustomAnalysis:        newCustomAnalysis(),
		cache:                 registry.NewCache(),
	}
}
func (im *IndexMapping) Validate() error {
	_, err := im.cache.AnalyzerNamed(im.DefaultAnalyzer)
	if err != nil {
		return err
	}
	_, err = im.cache.DateTimeParserNamed(im.DefaultDateTimeParser)
	if err != nil {
		return err
	}
	err = im.DefaultMapping.Validate(im.cache)
	if err != nil {
		return err
	}
	for _, docMapping := range im.TypeMapping {
		err = docMapping.Validate(im.cache)
		if err != nil {
			return err
		}
	}
	return nil
}
func (im *IndexMapping) AddDocumentMapping(doctype string, dm *DocumentMapping) {
	im.TypeMapping[doctype] = dm
}
func (im *IndexMapping) mappingForType(docType string) *DocumentMapping {
	docMapping := im.TypeMapping[docType]
	if docMapping == nil {
		docMapping = im.DefaultMapping
	}
	return docMapping
}