Add README.md

Author: hioki-daichi

kadai3-2/hioki-daichi/README.md

@@ -1 +1,80 @@
 # parallel-download
+
+## Overview
+
+`parallel-download` is a command that can download the resources on the web in parallel.
+
+Available options are below.
+
+| Option | Description                                                                          |
+| ---    | ---                                                                                  |
+| `-p`   | Download files in parallel according to the specified number. (default 8)            |
+| `-o`   | Save the downloaded file in the specified path. (Overwrite if duplicates.)           |
+| `-t`   | Terminate when the specified value has elapsed since download started. (default 30s) |
+
+## How to develop
+
+### 1. Install packages
+
+Execute `$ dep ensure` to install dependent packages.
+
+### 2. Start a dummy server
+
+Execute `$ ./bin/dummy_server.go` to start a dummy server that returns a Gopher image.
+
+```
+$ ./bin/dummy_server.go
+--------------------------------------------------------------------------------
+# Endpoint
+
+  GET /foo.png // Get a gopher image
+
+# Command-line options**
+
+  -failure-rate int
+        Probability to return InternalServerError.
+  -max-delay duration
+        Maximum time delay randomly applied from receiving a request until returning a response. (default 1s)
+  -port int
+        Port on which the dummy server listens. (default 8080)
+--------------------------------------------------------------------------------
+2018/09/30 00:25:05 Server starting on http://localhost:8080
+```
+
+### 3. Execute
+
+Execute the command with specifying the Gopher image endpoint of the dummy server (and some options).
+
+```
+$ go run main.go -p=3 -t=3s -o=bar.png http://localhost:8080/foo.png
+start HEAD request to get Content-Length
+got: Accept-Ranges: bytes
+got: Content-Length: 169406
+start GET request with header: "Range: bytes=112936-169405"
+start GET request with header: "Range: bytes=56468-112935"
+start GET request with header: "Range: bytes=0-56467"
+downloaded: "/var/folders/f8/1n0bk4tj4ll6clyj868k_nqh0000gn/T/parallel-download301219462/f4ec179a35"
+downloaded: "/var/folders/f8/1n0bk4tj4ll6clyj868k_nqh0000gn/T/parallel-download301219462/f8d59617fb"
+downloaded: "/var/folders/f8/1n0bk4tj4ll6clyj868k_nqh0000gn/T/parallel-download301219462/9e9b203414"
+concatenate downloaded files to tempfile: "/var/folders/f8/1n0bk4tj4ll6clyj868k_nqh0000gn/T/parallel-download301219462/814ff17dbf"
+rename "/var/folders/f8/1n0bk4tj4ll6clyj868k_nqh0000gn/T/parallel-download301219462/814ff17dbf" to "bar.png"
+completed: "bar.png"
+```
+
+## How to run the test
+
+```shell
+$ make test
+```
+
+## How to read GoDoc
+
+```shell
+$ make doc
+```
+
+## How to see code coverage
+
+```shell
+$ make cov
+```