Missing Git command when calling `go get` - go

Question

My Dockerfile
FROM golang:1.10.2-alpine3.7 AS build
RUN apk --no-cache add gcc g++ make ca-certificates
RUN apk add git
WORKDIR /go/src/github.com/meower
COPY Gopkg.lock Gopkg.toml ./
COPY util util
COPY event event
COPY db db
COPY search search
COPY schema schema
COPY meow-service meow-service
COPY query-service query-service
COPY pusher-service pusher-service
RUN go get -d -v ./...
RUN go install ./...
FROM alpine:3.7
WORKDIR /usr/bin
COPY --from=build /go/bin .
I added apk add git line.Without this line my docker-compose up produced
Step 13/17 : RUN go get -d -v ./...
---> Running in d917adba00cd
github.com/lib/pq (download)
go: missing Git command. See https://golang.org/s/gogetcmd
package github.com/lib/pq: exec: "git": executable file not found in $PATH
github.com/nats-io/go-nats (download)
go: missing Git command. See https://golang.org/s/gogetcmd
package github.com/nats-io/go-nats: exec: "git": executable file not found in $PATH
github.com/gorilla/mux (download)
go: missing Git command. See https://golang.org/s/gogetcmd
package github.com/gorilla/mux: exec: "git": executable file not found in $PATH
github.com/kelseyhightower/envconfig (download)
go: missing Git command. See https://golang.org/s/gogetcmd
package github.com/kelseyhightower/envconfig: exec: "git": executable file not found in $PATH
package github.com/retry: invalid github.com/ import path "github.com/retry"
github.com/segmentio/ksuid (download)
go: missing Git command. See https://golang.org/s/gogetcmd
package github.com/segmentio/ksuid: exec: "git": executable file not found in $PATH
github.com/gorilla/websocket (download)
go: missing Git command. See https://golang.org/s/gogetcmd
package github.com/gorilla/websocket: exec: "git": executable file not found in $PATH
github.com/olivere/elastic (download)
go: missing Git command. See https://golang.org/s/gogetcmd
package github.com/olivere/elastic: exec: "git": executable file not found in $PATH
With git line,other problems are still there
docker-compose up
Building pusher
Step 1/18 : FROM golang:1.10.2-alpine3.7 AS build
---> 44ccce322b34
Step 2/18 : RUN apk --no-cache add gcc g++ make ca-certificates
---> Using cache
---> 088fa5ba19a9
Step 3/18 : RUN apk add git
---> Running in 01022f57861b
WARNING: Ignoring APKINDEX.70c88391.tar.gz: No such file or directory
WARNING: Ignoring APKINDEX.5022a8a2.tar.gz: No such file or directory
ERROR: unsatisfiable constraints:
git (missing):
What does this mean?

Answer 1

go get internally calls the "reference" client-side tool of the particular VCS used to host the package to be fetched. In other words, go get by itself does not know how to interact with VCS servers.
So yes, in order to go get a package which is hosted by Git, you need the working Git installation providing a callable git binary.
As to your second problem, it does not appear to have anything related to Go, so I suggest you to do a bit of research and then ask a separate question tagged alpine if that fails.