ragserver: add ragserver-langchaingo variant

Change-Id: I76c6fc25ee8cf6a8c97ed23502b116aa3d3a6041
Reviewed-on: https://go-review.googlesource.com/c/example/+/608735
Reviewed-by: Ian Lance Taylor <[email protected]>
TryBot-Bypass: Eli Bendersky <[email protected]>
Reviewed-by: Eli Bendersky <[email protected]>
Auto-Submit: Eli Bendersky <[email protected]>

ragserver/README.md

@@ -31,6 +31,8 @@ Weaviate has the be installed locally; the easiest way to do so is by using
 
 * `ragserver`: uses the Google AI Go SDK directly for LLM calls and embeddings,
   and the Weaviate Go client library directly for interacting with Weaviate.
+* `ragserver-langchaingo`: uses [LangChain for Go](https://github.com/tmc/langchaingo)
+  to interact with Weaviate and Google's LLM and embedding models.
 
 ## Usage
 

ragserver/ragserver-langchaingo/go.mod

@@ -0,0 +1,70 @@
+module golang.org/x/example/ragserver/ragserver-langchaingo
+
+go 1.23.0
+
+require github.com/tmc/langchaingo v0.1.12
+
+require (
+	cloud.google.com/go v0.113.0 // indirect
+	cloud.google.com/go/ai v0.6.0 // indirect
+	cloud.google.com/go/aiplatform v1.67.0 // indirect
+	cloud.google.com/go/auth v0.4.1 // indirect
+	cloud.google.com/go/auth/oauth2adapt v0.2.2 // indirect
+	cloud.google.com/go/compute/metadata v0.3.0 // indirect
+	cloud.google.com/go/iam v1.1.7 // indirect
+	cloud.google.com/go/longrunning v0.5.7 // indirect
+	cloud.google.com/go/vertexai v0.10.0 // indirect
+	github.com/PuerkitoBio/purell v1.1.1 // indirect
+	github.com/PuerkitoBio/urlesc v0.0.0-20170810143723-de5bf2ad4578 // indirect
+	github.com/asaskevich/govalidator v0.0.0-20230301143203-a9d515a09cc2 // indirect
+	github.com/dlclark/regexp2 v1.10.0 // indirect
+	github.com/felixge/httpsnoop v1.0.4 // indirect
+	github.com/go-logr/logr v1.4.1 // indirect
+	github.com/go-logr/stdr v1.2.2 // indirect
+	github.com/go-openapi/analysis v0.21.2 // indirect
+	github.com/go-openapi/errors v0.22.0 // indirect
+	github.com/go-openapi/jsonpointer v0.19.6 // indirect
+	github.com/go-openapi/jsonreference v0.19.6 // indirect
+	github.com/go-openapi/loads v0.21.1 // indirect
+	github.com/go-openapi/spec v0.20.4 // indirect
+	github.com/go-openapi/strfmt v0.21.3 // indirect
+	github.com/go-openapi/swag v0.22.4 // indirect
+	github.com/go-openapi/validate v0.21.0 // indirect
+	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
+	github.com/golang/protobuf v1.5.4 // indirect
+	github.com/google/generative-ai-go v0.14.0 // indirect
+	github.com/google/s2a-go v0.1.7 // indirect
+	github.com/google/uuid v1.6.0 // indirect
+	github.com/googleapis/enterprise-certificate-proxy v0.3.2 // indirect
+	github.com/googleapis/gax-go/v2 v2.12.4 // indirect
+	github.com/josharian/intern v1.0.0 // indirect
+	github.com/mailru/easyjson v0.7.7 // indirect
+	github.com/mitchellh/mapstructure v1.5.0 // indirect
+	github.com/oklog/ulid v1.3.1 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
+	github.com/pkoukk/tiktoken-go v0.1.6 // indirect
+	github.com/weaviate/weaviate v1.24.1 // indirect
+	github.com/weaviate/weaviate-go-client/v4 v4.13.1 // indirect
+	go.mongodb.org/mongo-driver v1.14.0 // indirect
+	go.opencensus.io v0.24.0 // indirect
+	go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.51.0 // indirect
+	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.51.0 // indirect
+	go.opentelemetry.io/otel v1.26.0 // indirect
+	go.opentelemetry.io/otel/metric v1.26.0 // indirect
+	go.opentelemetry.io/otel/trace v1.26.0 // indirect
+	golang.org/x/crypto v0.23.0 // indirect
+	golang.org/x/exp v0.0.0-20230713183714-613f0c0eb8a1 // indirect
+	golang.org/x/net v0.25.0 // indirect
+	golang.org/x/oauth2 v0.20.0 // indirect
+	golang.org/x/sync v0.7.0 // indirect
+	golang.org/x/sys v0.20.0 // indirect
+	golang.org/x/text v0.15.0 // indirect
+	golang.org/x/time v0.5.0 // indirect
+	google.golang.org/api v0.180.0 // indirect
+	google.golang.org/genproto v0.0.0-20240401170217-c3f982113cda // indirect
+	google.golang.org/genproto/googleapis/api v0.0.0-20240513163218-0867130af1f8 // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20240509183442-62759503f434 // indirect
+	google.golang.org/grpc v1.64.0 // indirect
+	google.golang.org/protobuf v1.34.1 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)