Notifier

Considerations

To meet the requirements of the test I have made the following decisions:

Using the concurrency pipelines pattern, which in this case is composed by two stages connected by channels, which will allow concurrent processing (reading and sending) of STDIN messages.
Using a buffered channel in order to continue reading(not block the channel) the messages from the STDIN in case of the time interval for sending the messages is very high.
Creating an independent channel to store the errors of each stage and based on the information from this Google blog, merge the two channels, this allows it to monitor the result of the pipeline execution and control if I want to terminate the process (canceling the context) when one or more errors are found.
The number of errors allowed can be configured using the environment variable NOTIFIER_MAXALLOWEDERRORS.
Sharing the context with the gracefullyShutdown function to listen for the SIGINT signal and gracefully terminate the process by canceling the context.

Other aspects of the design of the solution:

Use of dependency inversion creating an interface for the HTTP client and passing it to the processor together with the file io.Reader interface for reading the STDIN.
The logs are categorized by level, it is possible to select the logging level of the service with the LogLevel environment variable.
It is possible to configure different aspects of the application through environment variables.
Unit tests are included.
Including Make as interface to execute commands to compile, test, check(linter) the program.
Docker configuration.

NOTIFIER_INTERVAL: Allows to set a default interval for sending notifications.
NOTIFIER_MAXALLOWEDERRORS:The application will terminate when it has reached this number of errors
NOTIFIER_LOGLEVEL:Log level
NOTIFIER_BUFFERSIZE:Buffer size for the message channel.
NOTIFIER_HTTPREQUESTTIMEOUT:Configuring the timeout time for the http client.
NOTIFIER_MAXIDLECONNS: controls the maximum number of idle(keep-alive) connections across all hosts.
NOTIFIER_MAXIDLECONNSPERHOST: restricts how many connections there are which are not actively serving requests.

make compile
./bin/notifier -u http://localhost:8080/notify < messages.txt -i 10ms

make make compile
docker build -t notifier .
docker run -i notifier -u http://localhost:8080/notify < messages.txt -i 200ms

make test

make check